APA (7th ed.) Citation

United States. Post Office Department. (1931). Postage on magazine covers returned to publishers. GPO.

Chicago Style (17th ed.) Citation

United States. Post Office Department. Postage on Magazine Covers Returned to Publishers. [Washington]: GPO, 1931.

MLA (9th ed.) Citation

United States. Post Office Department. Postage on Magazine Covers Returned to Publishers. GPO, 1931.

Warning: These citations may not always be 100% accurate.